1. Field of the Invention
The present invention relates to a recycling method, particularly to a method for recycling cutting fluid in the cutting industry of silicon wafer.
2. Description of the Related Art
Due to the fast development of the solar industry and the electronic industry, the requirement and performance of silicon chips is much more emphasized than ever. During the manufacture process of the silicon chip, a significant amount of wasted cutting fluid of silicon containing lots of debris from cutting tools and silicon bars may be generated, which may interfere with the quality of silicon chips if there is contamination of silicon oil.
Generally, silicon chips are obtained by continually cutting the silicon bar via a cutting tool, wherein the cutting tool generally consisting of carborundum is processed by providing a sustaining pressure to the silicon bar. During the cutting process, a cutting oil, mainly comprised of carborundum powders, polyethylene glycol (also called PEG), diethylene glycol (also called DEG) and cooling water, is used for regularly rinsing out the debris of cutting tool and silicon bar from the cutting tool. In this way, silicon chips with smooth cutting sections can be easily obtained. On the other hand, a great amount of wasted residue, such as cutting fluid of silicon, will be produced in the cutting process, which may lead to serious pollution if it is directly abandoned.
In the conventional art, the carborundum powders or silicon powders in the wasted cutting fluid of silicon can be recycled by separating the solid phase of the carborundum powders or silicon powders from the liquid phase of wasted fluid via a recycling method of centrifugal sedimentation. Otherwise, it is also sufficient to precipitate and isolate the colloid carborundum powder or silicon powder when adding a large amount of separating reagent to the wasted fluid.
However, there is no method for directly separating and recycling the cutting fluids from the wasted cutting fluid of silicon described above. Hence, it is necessary to provide a method for recycling cutting fluid.